1. Field of the Invention
The present invention relates to a device for liquid development in a reproduction machine which is operated on a sheet by sheet basis. More particularly, this invention relates to a method and device for developing electrostatic latent images on a sheet surface with a developer having a liquid developing system.
Such a developer may be an autonomous unit but, preferably, it is incorporated in a combined reproduction machine having associated exposure devices and development devices. It is particularly appropriate for incorporation into a reproduction machine which is operated on sheet by sheet basis, in which the original and the copy sheet are stationary and in parallel planes during exposure. The exposure is preferably performed by back and forth movement in a plane parallel to that of the sheets by a mobile unit which especially carries a lamp and optic system.
2. Discussion of the Prior Art
Known liquid development systems operate, in general, either by immersion of the sheet to be developed into a tank that contains a liquid developer which is kept agitated, or by application of the liquid to the sheet by means of rollers. The first mentioned system has the drawback of excessively wetting the paper and requiring the use of a drying system. The second mentioned system does not easily lend itself to the development of separate sheets.
U.S. Pat. No. 3,367,791 of Lein provides a roller dipping into a liquid bath, which roller is operated at speeds such that a hydrodynamic pressure is created against the surface of the sheet, holding the latter against a back guide which is located at a fixed, determinate spacing from the closest point of roller approach. The roller is made conductive, or at least has a highly conductive surface layer, which provides the field control effect required at the point where electrostatic deposit of particles is occurring. The motion of the roller in addition to providing the hydrodynamic forces for sheet control, also renders the liquid action sufficiently turbulent to provide a constant changing and replenishing action which will forestall the possibility of the developing liquid's reaching a starved or depleted condition at the developing location where rapid particle deposit is occurring due to the presence of the highly efficient field control.
U.S. patent application, Ser. No. 537,600, filed Dec. 30, 1974, of Pham Kim Quang, et al, provides a device which makes it possible to assure sheet by sheet development of electrophotographic papers, having the photoconductive face turned upward, and at the same time permits the development to take place by the sufficiently prolonged action of a constantly renewed and enriched liquid developer under the action of a suitably arranged electric field.